Municipal and agricultural waste disposal is a major problem. Feedlots, animal barns, agroindustrial plants, municipal sewage, and farms that keep large numbers of animals are sources of enormous quantities of organic waste. The disposal of untreated organic waste causes serious pollution problems which include those tied to the wastes high content of chemically oxidizable components, expressed as COD or chemical oxygen demand, and BOD, biological or biochemical oxygen demand. When these pollutants reach bodies of water, either because they leach from disposal sites or as a consequence of being directly released or transported into water bodies, they deoxygenate the receiving waters and impair the receiving waters' capability to support aquatic life.
Acidity and high pathogen content add to the COD and BOD problems of untreated waste disposal. Acrid gases released into the atmosphere are not only unpleasant but they can also contribute to acid deposition, global greenhouse effects, and ozone depletion.
For agricultural animals, the animals are confined in high densities and lack functional and sustainable waste treatment systems. The liquid wastes are generally treated in large anaerobic lagoons with intermittent disposal through land applications (Stith, P. and Warrick, J., Boss Hog, North Carolina's pork revolution, The News & Observer, 1-3, Feb. '9-26, 1995; USEPA, Proposed regulations to address water pollution from concentrated animal feeding operations, EPA 833-F-00-016, January 2001, Office of Water, Washington, D.C., 20460). This system was developed in the early and mid-20th century prior to the current trend in high concentrated livestock operations. One of the main problems in sustainability is the imbalance of nitrogen (N) and phosphorus applied to land (USEPA, supra; Cochran et al., Dollars and Sense: An economic analysis of alternative hog waste management technologies, Environmental Defenses, Washington D.C., 2000). Nutrients in manure are not present in the same portion needed by crops, and when manure is applied based on a crop's nitrogen requirement, excessive phosphorus is applied resulting in phosphorus accumulation in soil, phosphorus runoff, and eutrophication of surface waters (Heathwaite et al., A conceptual approach for integrating phosphorus and nitrogen management at watershed scales, J. Environ. Qual., Volume 29, 158-166, 2000; Sharpley et al., Practical and innovative measures for the control of agricultural phosphorus losses to water: An overview, Journal Environ. Qual., Volume 29, 1-9, 2000; Edwards and Daniel, Environmental impacts of On-Farm Poultry Waste Disposal-A Review, Bioresource Technology, Volume 41, 9-33, 1992).
Conservation and recovery of nitrogen (N) and phosphorus from wastes is important in agriculture because of the high cost of commercial fertilizers. One of the largest environmental concerns with livestock and poultry production is the loss of ammonia gas (NH3) from manure (Aneja et al., Measurement and analysis of atmospheric ammonia emissions from anaerobic lagoons, Atmos. Environ., 35, 1949-1958, 2001; Paerl, Coastal eutrophication and harmful algal blooms: Importance of atmospheric deposition and groundwater as “new” nitrogen and other nutrient sources. Limnol. Oceanogr. 42, 1154-1165.1997) Phosphorus (P) build-up in soils to excessively high levels due to animal manures often results in eutrophication and pollution of surface waters. Nutrient pollution in the waterways is one of the United States' most challenging environmental problems. It is caused by too much nitrogen and phosphorus runoff or discharges into the environment. Nutrient pollution has diverse and far-reaching effects on the economy of the United States, impacting many sectors that depend on clean water. The U.S. tourism industry loses about $1 billion each year, mostly from losses in fishing and recreational activities because of nutrient-polluted water bodies. As a result of phosphorus pollution, algal blooms in drinking water sources can drastically increase treatment costs and shortages in water supplies.
Phosphorus (P) build up in soils to excessively high levels due to animal manures often results in eutrophication and pollution of surface waters. Therefore, the ability to extract phosphorus from manure will be critical to the ability to accomplish waste utilization through land application without elevating soil phosphorus levels. Production of biogas from manure using anaerobic digesters (AD) is projected to be important in the future. If a new technology could be developed to recover concentrated phosphorus from AD effluents that can be removed from the watershed, then producers will also benefit from the sale of water quality credits in emerging nutrient credit programs being established through the United States of America. Another environmental and regulatory concern is the excess nitrogen (N) from the manure in confined livestock production, so farmers will be much more willing to adopt new technology for manure that addresses phosphorus and nitrogen in conjunction.
U.S. Pat. No. 6,1777,077 (Lee et al.) and U.S. Pat. No. 6,200,469 (Wallace) both relate to the removal of nitrogen and phosphorus from wastewater wherein the phosphate is removed using microorganisms in aerobic tanks which absorb the phosphorus released from denitrified wastewater. See also U.S. Pat. No. 6,113,788 to Park et al; U.S. Pat. No. 6,117,323 to Haggerty; U.S. Pat. No. 6,139,743 to Park et al.
U.S. Pat. No. 6,893,567 (Vanotti et al.) is directed to a system for treating wastewater to at least reduce the amount of ammonia and phosphorus, as well as reducing the presence of infectious microorganisms by using a nitrification step to reduce or eliminate carbonate and ammonium buffers contained in the wastewater, precipitating phosphorus using an alkaline earth metal and increasing the pH of the wastewater. See also U.S. Pat. No. 7,674,379 (Vanotti et al.).
Szogi et al. developed a treatment process to recover nutrients from animal wastes. The process extracts phosphorus from solid animal wastes such as, for example, poultry litter or animal manure solids (Szogi et al., U.S. Pat. No. 8,673,046, Mar. 18, 2014). The first step of this process extracts phosphorus from solid animal wastes using mineral or organic acids. In the second step, phosphorus is recovered by the addition of liquid lime and an organic poly-electrolyte to the liquid extract to form a calcium-containing phosphorus precipitate.
While various systems have been developed for removing NH3 and phosphorus from wastewater, there still remains a need in the art for different abatement systems that removes both NH3 and phosphorus and recovers both in a concentrated pure form. The present invention, different from the related art,—provides such systems 20 using hydrophobic gas-permeable membranes and circulated stripping solutions to produce an effluent that can be treated with phosphorus precipitating compounds to recover up to 100% of the phosphorus present in wastewater.